Distributed lighting system with fiber optic controls

ABSTRACT

A vehicle lighting system includes one or more central light sources, a plurality of optical loads including headlight lenses, an optical fiber network that extends from the light sources to illuminate the headlight lenses and other optical loads, and optical switches and oscillators that include respective input fibers illuminated from the light source and output fibers to respective optical loads, and operate by enabling and disabling optical connections between their input and output fibers. The headlight assemblies switch between high and low beams by moving their fibers vertically, and control beam diffusion by moving the fibers parallel to the lens axes, including an automatic diffusion adjustment for a headlight reflection from a vehicle in front. The switches include various mechanisms for moving the input and output fibers into and out of alignment with each other, including a shaped resilient sleeve, a hinge pivotally joining the fibers, an opaque shutter with a transmissive section movable between the fibers, and also a liquid-based switch that relies upon total internal reflection. A feedback mechanism for some of the switches dims the source lamp when the switch is OFF to conserve energy. The oscillators operate by normally urging an input fiber towards an OFF position, at which it actuates a mechanism that shifts it to an ON position at which the mechanism is deactivated. A failsafe system employs multiple light sources, with each source sharing its light output with the load for another source that has failed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to distributed lighting systems, particularly forroom lighting and vehicles, in which optical fibers distribute lightfrom a central source to a number of different optical loads, with thefibers performing various control functions such as switching,oscillation and headlight beam control.

2. Description of the Related Art

Conventional automobile lighting systems use separate light bulbs foreach lighting function, resulting in some cases in more than one hundreddifferent light bulbs. This is not a desirable situation for energyefficiency and reliability. Furthermore, some of the bulbs are typicallyplaced in inconvenient locations, making them difficult to access andincreasing maintenance costs, especially for instrument panel lightings.The bulbs are powered by an electrical wiring network, leading to thepossibility of electrical short circuits that are often difficult tolocate. The light bulb systems are also subject to breakage in case ofimpacts, and add to the weight, bulk and expense of the overall vehicle.

An alternate system in which light is distributed from a central lightsource to various optical loads within a vehicle by means of "lightbusses" is described in U.S. Pat. No. 4,930,049 to Davenport et al. Thelight bus network includes a number of optical control functions, suchas a switch, turn signal oscillator and dimmer. All of these devices,however, are subject to improvement. In the optical switch, for example(FIG. 9(b) of the '049 patent), a receiving optical fiber is moved intoand out of alignment with a light bus by means of a piezoelectric,electromagnetic, pneumatic bimetal or memory metal mechanism. All ofthese involve a simple bending of the receiving fiber away from thelight bus to turn the switch OFF. This does not account for the factthat light typically spreads out when emitted from the end of an opticalfiber, and no mechanism is provided for positively blocking thetransmission of light from the light bus to the receiving fiber in theOFF position. Furthermore, the system operates "open loop" in the sensethat there is no mechanism to confirm that the fiber has been properlypositioned.

In the turn signal oscillator of the '049 patent (FIG. 10(b)), the lightbus is moved by an externally controlled mechanical rotating arm intoand out of alignment with a receiving "optical carrying member".However, no mechanism is provided to assure that the light bus moves allthe way into and then out of alignment with the receiving opticalcarrying member.

In FIG. 11(b) of the patent, an optical dimming mechanism is disclosedin which a "means" 78 in the optical path alters its transparencybetween substantially clear and substantially cloudy. However, themanner in which this function is accomplished is not described.

A distributed lighting system in which light from a central light sourceis carried by a series of optical fibers to an array of headlight lensesis described in U.S. Pat. No. 4,868,718 to Davenport et al. In thispatent the ends of the fibers are held stationary in alignment withtheir respective lenses, while optical wedges or rotating flat membersare inserted between the fibers and their respective lenses to shiftbetween high and low beams. In a related system described in U.S. Pat.No. 4,949,227 to Finch et al., a movable mask is placed between thefibers and the headlight lenses to form either a high or a low beampattern, depending upon the position of the mask. Both of theseapproaches require the insertion of additional mechanical devicesbetween the fibers and the headlight lenses, thus adding to the cost andcomplexity of the system.

Another headlight system is described in U.S. Pat. No. 4,811,172 toDavenport et al. in which each headlight has a dedicated light source,with separate optical fibers transmitting light from the source to thevarious lenses of the headlight. A pair of fibers are provided for eachlens and are arranged at an angle to each other, with one fiber on thelens axis and the other off-axis. One of the fibers is illuminated toproduce a high beam output, and the other to produce a low beam output.This system requires a redundancy in the optical fibers for eachheadlight lens, and also requires a separate lamp for each headlight.

A light source for a distributed vehicle lighting system is described inU.S. Pat. No. 4,958,263 to Davenport et al. The source consists of apressurized lamp with quartz light guides merged into portions of itsouter surface to provide illumination for the various optical loadswithin the vehicle. The portions of the lamp that are not merged withthe light guides are coated with a diffusive reflective coating that issaid to substantially prevent light from being transmitted through thecoating, thereby directing all of the light generated by the lamp intothe light guides. However, the patent does not describe any controlmechanisms such as optical switches or oscillators. A headlight systemis shown, but no mechanism for alternating between high and low beams ispresented.

While the centralized lighting systems described in the above patentsoffer advantages over conventional discrete lighting systems, there isalso a significant potential reliability problem. If the central lightsource fails, all or a large section of the lighting system will belost. The problem is more severe than in discrete lighting systems, inwhich the loss of a light bulb affects only its single associatedcomponent. The described systems do not provide a failsafe mechanism toprevent a severe disruption of the lighting system when the light sourcefails.

SUMMARY OF THE INVENTION

The present invention provides a central lighting source with a fiberoptic distribution network that is suitable for automobiles, roomlighting systems and other applications in which distributed opticalloads are supplied by a central light source. Light is provided from acentral light source to a number of different optical loads through thefiber network. It offers a more convenient access to the light sources,reduced maintenance costs, higher energy efficiency and reliability, areduction in the likelihood of short circuits in electrical lead wires,light weight, compactness and high impact resistance, as compared todiscrete lighting systems. It also provides improved control mechanismssuch as optical switches, modulators and headlight controls, and afailsafe system for the central lighting source, that go beyond thedistributed lighting systems in the patents mentioned above.

The distributed lighting system includes a central light source, anumber of different optical loads including a plurality of headlightlenses, and an optical fiber network that extends from the central lightsource to provide illumination for the headlight lenses and the otherloads. One or more optical switches are included in the network, witheach switch having an input fiber from the light source and an outputfiber to an optical load. The switches operate by selectively enablingor disabling an optical connection between their respective input andoutput fibers. One or more optical oscillators are also included, eachhaving an input fiber from the light source and an output fiber to anoptical load. The oscillators operate by oscillating between states thatalternately enable and disable optical connections between their inputand output fibers.

In the headlight assemblies, each headlight lens is illuminated by arespective optical fiber. The positions of the fibers are adjustedrelative to the lenses to control the nature of the headlight beam. Thefibers can be moved up or down to switch between high and low beams, andtoward or away from the lenses to adjust the beam collimation. Thefibers are preferably held in a common mounting member, and a motor canbe provided to adjust the position of that member. In a "smart" version,reflections of the headlights back from a car in front are sensed by anoptical detector that responds to a wavelength of the headlight beamwhich is significantly different from the tungsten lamps, and the sensedreflections used to move the fibers closer to the lenses to diffuse theheadlight beam. A pair of spaced optical detectors can be used todiscriminate between light reflected back from the front and light froman oncoming vehicle in an adjacent lane, and to diffuse the headlightonly for the first case.

Various embodiments of an improved optical switch provide for morereliable switching operation. In each embodiment an input fiber provideslight from a central source, while an output fiber delivers the light toan optical load. In a first embodiment, a first one of the fibers ishoused in a shaped sleeve that includes two stable positions for thefiber. A resiliently deformable section that couples the two stablepositions allows movement of the first fiber therebetween, andreleasably retains the first fiber in its current stable position. Thefirst fiber is aligned with the second fiber at one but not the other ofits stable positions, and a mechanism is provided to move the firstfiber through the deformable sleeve section between the sleeve'sbistable positions. The sleeve, including the coupling section, ispreferably formed from a unitary elastic material, with a rigid innersleeve around the first fiber within the shaped sleeve.

In another switch embodiment the input and output fibers are secured bya hinge for rotation between an ON position at which the fibers arealigned and adjacent to each other, thereby coupling light from theinput into the output fiber, and an OFF position at which the ends ofthe fibers are separated. An opaque shutter is inserted between thefiber ends in the OFF position, and withdrawn in the ON position. Theshutter is preferably mounted on a spring biased plunger that ispivotally coupled to the input and output fibers by means of push rods,with the push rods rotating the fiber ends apart when the plunger isdepressed to insert the shutter between them. To prevent reflectionlosses that might otherwise result from gaps between the fiber ends whenthe switch is ON, a liquid with a refractive index that is substantiallymatched to that of the fibers may be sealed between the fiber ends.

Another switch embodiment employs an opaque shutter with a generallytransmissive section between the ends of the input and output fibers.The shutter is moved so that it either blocks or permits thetransmission of light between the two fibers. Respective gradient indexrod lenses are positioned between the shutter and each of the fibers toexpand a light beam from the input fiber, and then contract the beamback into the output fiber, after its transmission through thetransmissive shutter section. The lenses reduce light losses that wouldotherwise occur from the fanning of a light beam emitted from the inputfiber. The transmissive section can be implemented as a color filter,and the shutter can be moved to intermediate positions between theswitch OFF and ON positions to provide a dimming capability. The switchis preferably implemented in a housing that has intersecting fiber andshutter bores. The shutter is held between a pair of pistons in theshutter bore, and the fibers are held by a pair of pistons in the fiberbore. The position of the shutter pistons and their attached shutter canbe controlled either by a mechanical mechanism, or by electromagnetswithin the shutter bore that act upon the magnetic shutter pistons.

To conserve energy when the above switches are OFF and their opticalloads are not being served, a feedback mechanism can be provided toreduce the intensity of the light source. This preferably consists of areflector that is illuminated by the input fiber in its OFF position,and reflects the emitted light back through the input fiber to thevicinity of the light source. There it is extracted and used to lowerthe energization of the light source.

Another switch embodiment employs a generally optically transmissivehousing that has a predetermined refractive index and an internalcavity. Light is transmitted through the cavity between input and outputoptical fibers. Liquid from a reservoir can be moved into and out of thelight path through the cavity. The cavity has a wall that faces theinput fiber at a predetermined angle; that angle and the liquid'srefractive index are selected so that light is transmitted through thecavity between the input and output fibers when the liquid is in thecavity light path, but is reflected by total internal reflection at thecavity wall and prevented from reaching the output fiber when the liquidis removed from the cavity.

A novel optical oscillator is also described to provide intermittentillumination for a turn signal or the like. An input fiber from thecentral light source illuminates an output fiber to the optical load inan ON position, and illuminates an optical detector in an OFF position.The input fiber is urged towards its OFF position, preferably by aspring or a bimetallic strip. Illumination of the photodetector actuatesa mechanism, such as an electromagnet or heating of a bimetallic strip,to move the input fiber to its ON position; the photodetector ispreferably a solar cell that directly provides the electrical energy forthis function. In the ON position the light is directed away from thephotodetector, which deactivates it and allows the input fiber to returnto the OFF position. The input fiber thus oscillates between its ON andOFF positions.

A failsafe system is also provided for the central light source in theform of two light sources that are connected by respective sets ofoptical fibers to respective sets of optical loads. Beam splitters thatare normally held out of the operative light paths are actuated todivert a portion of the light from one source to the loads for the othersource when the other source fails. In the preferred embodiment aseparate beam splitter is provided for each light source. The beamsplitters each have a first non-actuated position, a second position atwhich they divert a portion of the light from their respective sourcesto the optical loads for the other source, and a third position at whichthey direct light diverted from the other source to their own opticalloads. When one beam splitter is in its second position the other is inits third position, and vice versa. The output intensities of the lightsources are preferably adjustable, and the intensity of the survivingsource is increased in response to a failure of the other source.

These and other features and advantages of the invention will beapparent to those skilled in the art from the following detaileddescription, taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a distributed automobile lighting systemfrom a central light source in accordance with the invention;

FIG. 2 is a perspective, partially block diagram of a headlight controlsystem that forms part of the invention;

FIG. 3 is an elevational view of an alternate headlight control system;

FIGS. 4 and 5 are respectively elevational and sectional views of oneembodiment of an optical switch in accordance with the invention;

FIG. 6 is a block diagram of a light source adjustment system that canbe used in connection with the switch of FIGS. 4 and 5;

FIG. 7 is a sectional view of another optical switch embodiment;

FIG. 8 is an elevational view of a third optical switch embodiment;

FIG. 9 is a elevational view of a shutter used with the switch of FIG.8;

FIGS. 10a and 10b are sectional views of an optical switch that uses theconcept of the FIG. 8 switch, with a preferred mechanical structure; Theswitch of FIG. 10a does not include GRIN lenses; the switch of FIG. 10bincludes GRIN lenses;

FIG. 11 is a perspective view of an alternate shutter structure for theswitch of FIG. 10;

FIG. 12 is a sectional view of another optical switch embodiment;

FIG. 13 is a sectional, partially block diagram of an optical oscillatorin accordance with the invention;

FIG. 14 is an elevational, partially block diagram of an alternateoptical oscillator; and

FIG. 15 is a block diagram of a failsafe central light source for adistributed lighting system.

DETAILED DESCRIPTION OF THE INVENTION

A block diagram of a distributed lighting system for an automobile isshown in FIG. 1. While automobiles are believed to be a significantapplication, the invention is not limited to automobiles and is alsoapplicable to room lighting, other types of vehicles and environments inwhich multiple optical loads can be serviced from a central lightsource.

The system uses a small number of light sources, preferably long lifemetal halide high intensity discharge (HID) lamps 2a and 2b, to serviceall of the optical requirements for an automobile. While two separatelight sources are illustrated, more sources or only one could also beused. However, at least two sources are preferred to provide a failsafemechanism, described below in connection with FIG. 15, in case one ofthe lamps should fail.

The system of FIG. 1 is illustrated as having multiple optical loads,including right and left headlights 4R and 4L, right and left taillights 6R and 6L, right and left front directional (turn) signals 8R and8L, right and left rear directional (turn) signals 10R and 10L, aninstrument panel light 12 and an overhead dome light 14. Additionaloptical loads, such as brake and trunk lights, would also be present,but have been omitted for simplicity since they would be serviced in amanner similar to the functions illustrated in FIG. 1.

The HID lamp 2a is shown illuminating a number of different opticalfibers that supply illumination for the directional lights, instrumentpanel and overhead light, while lamp 2b illuminates optical fibers thatsupply the headlights and tail lights. Specifically, the first lamp 2ailluminates the input ends of optical fiber bundles 16R and 16L, whichare respectively connected through optical oscillators 18R and 18L tothe right and left sets of front and rear turn signal lights. The lamp2a also illuminates the input end of an optical fiber 20 that isconnected through an optical ON-OFF switch 22 for the overhead domelight 14, and the input end of another optical fiber 24 that isconnected through a dimmer switch 26 for the instrument panel 12. Thesecond lamp 2b illuminates the input ends of optical fibers 28R, 28L,30R and 30L, which are respectively connected through ON-OFF opticalswitches 32R, 32L, 34R and 34L to the right and left headlights and theright and left tail lights.

Novel and improved designs for the optical switches, oscillators anddimmer, and also for the headlight assemblies, are provided by theinvention. Referring first to the headlight assemblies 4R and 4L, apreferred design for each assembly is illustrated in FIG. 2. Eachheadlight consists of a linear array of Fresnel lenses 36. An inputoptical fiber bundle 38 includes a separate fiber for each lens; fourseparate input fibers 38a, 38b, 38c and 38d are illustrated. The end ofeach fiber is preferably held in a common mounting block 40, and aremoved in common by a stepper motor 42 that is connected to adjust theposition of the mounting block. The motor 42 is preferably capable ofadjusting the position of the mounting block in three axes: verticallyto switch between high and low headlight beam outputs; towards and awayfrom the lenses to adjust the collimation of the output beam; andlaterally if a lateral beam adjustment capability is desired.

Each of the fibers 38a-38d is aligned with and illuminates acorresponding lens 36a-36d. The fibers are normally positioned slightlyabove the lens focal axes and about a focal length behind the lenses toproduce a low beam output that is directed slightly below horizontal. Toswitch to a high beam, the motor 42 moves the mounting block verticallydownward until the fibers are approximately on the lens focal axes. Thisraises the output headlight beam to approximately horizontal. Withconventional headlight lenses, which have both diameters and focallengths of approximately 2.5 cm, a vertical travel on the order of 0.25cm between the low and high beam fiber positions will normally beappropriate.

In a "smart" version of the headlight assembly, when the vehicle is inheavy traffic the reflection of the headlight beam from the tail of thecar directly in front is detected and used to move the input fiberstowards their respective lenses, thus diffusing the headlight beam,and/or to switch from high to low beams. This is also desirable for anoncoming vehicle in the opposing lane, until the oncoming vehicle isabout to pass the car. On the other hand, when the car is on an openroad the light beam can be adjusted to provide stronger and moredirectional lighting for better driving visibility. To distinguishbetween reflected light from a vehicle in front or a distant oncomingvehicle, and light from the headlights of an oncoming vehicle that isabout to pass and no longer needs the diffused and/or low beams, a pairof photodetectors 44a and 44b may be used, with the two photodetectorslaterally spaced from each other. Since one of the photodetectors willbe significantly closer than the other to an oncoming vehicle that is tothe side of the car and just about to pass, it will receive a strongerlight intensity from the oncoming vehicle's headlights than the otherphotodetector. Any differences in the optical intensities of I1 and I2reaching the two photodetectors is sensed by a differential detector 46,which responds by preventing the motor 42 from moving the fibers towardstheir respective lenses and/or lowering the beams when the ratio exceedsa preset value R. However, a headlight beam reflected from a vehicledirectly in front or from a more distant oncoming vehicle will bereceived by the two photodetectors at the same intensity level. In thisevent the motor 42 will be actuated to move the fibers towards theirrespective lenses and thereby diffuse the headlight beam and/or to movethe fibers up to lower the beams.

To prevent a diffusing of the headlights in response to the brake lightsfrom a vehicle in front or some other non-headlight source, thephotodetectors 44a and 44b can be made sensitive to a particular opticalwavelength that is included in the headlight beams, but is not presentin red or other non-headlight colors. The metal halide lamps that aretypically used for headlights have a well defined short wavelengthemission spectrum, including a line at approximate 4,000 Angstroms inthe blue region. Making the photodetectors sensitive only to this orsome other desired headlight wavelength will prevent them from actuatingthe motor in response to other colors. For a 2.5 cm focal lengthheadlight lens, a horizontal fiber travel on the order of 1.2 cm willnormally provide a suitable amount of diffusion. Conversely, the fiberscan be moved backward away from their respective lenses, therebyincreasing the collimation of the headlight beams, if there is notraffic in front of the vehicle as indicated by a lack of any headlightreflections.

A modification of the described headlight assembly is shown in FIG. 3.In this embodiment the input fiber 38a for a given headlight lens 36ailluminates one or the other of two output fibers 48a and 48b. Outputfiber 48a is positioned to illuminate the lens so that a high beam isproduced, while output fiber 48b is located above fiber 48a andilluminates the lens to produce a low beam. An electro-mechanical switch50 is used to move the input fiber 38a between alignments with the twooutput fibers, and thus switches between high and low beam settings. Thehigh beam setting for input fiber 38a is indicated in solid lines, whilethe low beam setting is indicated in dashed lines. Again, the inputfibers for each of the headlight lenses are preferably mounted in acommon mounting block and moved together as a unit.

Turning now to FIGS. 4 and 5, an improved optical ON-OFF switch that canbe used in a distributed lighting system such as that of FIG. 1 isshown. The switch includes an input fiber 52a that receives light from acentral source, and an output fiber 52b that supplies one of thevehicle's optical loads. The input fiber is held in either one or theother of two bistable positions by means of a shaped sleeve 54. TheON-OFF action is accomplished by holding one of the fibers stationaryand moving the other fiber into and out of alignment with the first one.For this purpose the sleeve 54 has a generally figure-eight shape thataccommodates the movable fiber at each end or chamber of thefigure-eight. A deformable section 56 is provided between the sleeve'stwo end sections; it is sufficiently elastic so that the movable fibercan be shifted from one chamber of the figure-eight to the other bypushing the walls of the deformable section outward. The section thenresiliently returns to its original shape to releasably retain the fiberin its new position. The sleeve 54 is most conveniently provided withthe entire figure-eight shape formed from a unitary elastic material.

In the illustration if FIGS. 4 and 5, the input fiber 52a is movablebetween the two sleeve chambers, while the output fiber 52b remainsstationary in the lower chamber. A suitable switch control for switchingthe input fiber between the upper and lower chambers, such as aspring-loaded plunger 58 that is coupled to the moving fiber via a rigidsleeve 60, allows the switch to be set either ON with the two fibersaligned, or OFF with the input fiber shifted to the upper chamber(indicated in dashed lines in FIG. 4). Once the input fiber is forcedinto one chamber it remains in that location, and hence the designation"bistable".

The described switch can be coupled with an energy saving mechanism thatreduces the output of the source lamp when the switch is in its OFFposition. This technique employs a reflective surface 62 (shown in FIG.4) that faces the input fiber 52a within the sleeve chamber that is notoccupied by the output fiber 52b. The manner in which the reflected beamis used to reduce the source lamp intensity is illustrated in FIG. 6.After reflection in the switch, the light traveling through the inputfiber 52a returns back through that fiber to the vicinity of the sourcelamp 2b. There it is extracted by a mechanism such as a one-way mirror64 that transmits light from the lamp 2b into the fiber, but deflectslight returned back from the fiber. The deflected light is sensed by anattenuator 66 that reduces the intensity of the lamp 2b by a desiredamount. The lighting system can thus be actively managed for maximumpower efficiency.

An alternate switch design is shown in FIG. 7. In this embodiment, theinput and output fibers 52a and 52b are surrounded by respective rigidsleeves 68a and 68b, with a hinge 70 fixedly mounted and connecting thetwo sleeves together at a pivot point. An opaque shutter 72 is carriedby a spring-biased plunger 74, which in turn is connected to theopposite sides of the sleeves 68a and 68b by means of respective pushrods 76a and 76b. The push rods are pivotally connected at theiropposite ends to the plunger and to their respective fiber sleeves, suchthat depressing the plunger causes the sleeves 68a and 68b to pivot awayfrom each other about hinge 70 and the shutter 72 to be inserted betweenthe fibers 52a and 52b, while lifting the plunger withdraws the shutterfrom between the fibers and rotates the two sleeves closed to align thefibers with each other. The switch is thus ON with the input fiber 52aaligned with and transmitting light to the output fiber 52b when theplunger is raised, and OFF with the shutter 72 deflecting light from theoutput fiber 52b when the plunger is depressed. As with the switch ofFIGS. 4 and 5, the plunger can be either mechanically orelectro-mechanically activated.

To reduce optical reflection losses in case small gaps are presentbetween the adjacent ends of the input and output fibers 52a and 52b,the switch shown in FIG. 7 is preferably sealed within a liquidreservoir 78. The reservoir is flooded with a liquid 80 that has arefractive index which is substantially matched to that of the fibers;for plastic fibers a suitable liquid is optical gel no. 0607 or 0608from Cargille Laboratories, Inc., with a refractive index of 1.457. Theliquid fills in any gaps that may be left between the aligned ends ofthe fibers when the switch is ON, and thus provides a substantiallycontinuous optical path between the input and output fibers.

Another optical switch embodiment is shown in FIGS. 8 and 9. Thecontrolling portion of this switch is a movable shutter 82 that can beeither manually or electro-magnetically moved to enable or block opticaltransmission between the input and output fibers 52a and 52b. Theshutter is formed from a thin opaque material, such as a metal pieceabout 200 microns thick. For manual operation, the shutter preferablyhas a spring-loaded mechanism 84 that locks the shutter in place whendepressed, and releases it when depressed a second time.

The shutter includes a generally transmissive section 86 that ispreferably about the diameter of the fibers. The shutter is moved toposition the transmissive section 86 in alignment with the input andoutput fibers to turn the switch ON, and then displaced so that theopaque shutter material blocks light transmission between the two fibersto turn the switch OFF. The transmissive section 86 can include a colorfilter if coloration is desired for the light transmitted to the outputfiber 52b as shown by shading in FIG. 9.

Since the light emitted from the end of the input fiber 52a normallyfans out, some of this light will be lost from the output fiber evenwhen the switch is ON. To reduce this loss, and also to relax the needto position the two fibers very close to each other as well as have themhighly aligned, a pair of gradient index (GRIN) rod lenses 88a and 88bcan be positioned respectively between the end of input fiber 52a andthe shutter, and between the shutter and the end of output fiber 52b.When assembled in the switch with opposite orientations, the action ofthese two lenses is to expand a light beam emitted from the input fiber,and then to contract the expanded beam back into the output fiber. Forthis purpose the transmissive shutter section 86 should be enlarged toaccommodate the expanded beam.

The use of the sliding shutter can easily be used to add a dimmerfunction to the switch. The mechanical or electro-mechanical shuttercontrol needs merely to be able to move the shutter to intermediatepositions between full ON and full OFF to make it a dimming switch. Thisis useful, for example, in connection with instrument panelillumination.

Preferred implementations are shown in FIGS. 10a and b and 11 for theswitching concept of FIGS. 8 and 9. A housing is provided that allowsfor a very convenient assembly and adjustment of the operative switchelements. The solid housing 90 has a pair of intersecting bores, onebore 92a for the optical fibers and the other bore 92b for the shutter.The input and output fibers 52a and 52b are carried by respectivepistons 94a and 94b that are slidingly lodged within the fiber bore 92aon opposite sides of its intersection with the shutter bore 92b. The twofibers are held in alignment with each other so that light emitted fromthe input fiber illuminates the output fiber when the switch is ON.

Within the shutter bore 92b, the shutter 82 is held between pistons 96aand 96b on opposite sides of the bore intersection. For electro-magneticshutter control such as the use of electromagnets 98a and 98b at theopposite ends of the shutter bore, the shutter pistons are formed from amagnetic material. Alternately, a mechanical control can be provided foradjusting the shutter position. In this event the shutter pistons can beextended to the length of pistons 96a' and 96b' as shown in FIG. 11, sothat the end of one piston extends out of one end of the bore while theend of the other piston is flush with the other end of the bore. Asshown in FIG. 10b, GRIN lenses 91 could also be used in thisconfiguration.

An additional switch embodiment is illustrated in FIG. 12. This switchis based upon the optical phenomenon of total internal reflection. Inputand output fibers 52a and 52b are optically coupled to a transparenthousing 100, either by positioning the ends of the fibers next to thehousing or by inserting them into insets (not shown) within the housing.The fibers are aligned with each other such that a beam emitted from theinput fiber 52a will reach the output fiber 52b unless interrupted bythe switch. The main body of the housing preferably comprises a pair ofprisms 102a and 102b that are formed from the same material, and haveangled surfaces 104a and 104b that are spaced apart within the housingto form a cavity. A reservoir 106 that is shown within the housing, butcan also be provided externally and coupled into the housing throughappropriate tubing, opens to the cavity 108 and stores a generallytransmissive liquid 110. A mechanism, such as a spring-biased piston112, is provided to move liquid from the reservoir into and out of thecavity 110. The angle of the prism wall 104a relative to the opticaltransmission path between the fibers 52a and 52b, and the liquid'srefractive index, are selected such that light emitted by the inputfiber 52a is transmitted through the cavity to the output fiber 52b whenthe liquid is in the optical path within the cavity, but is reflected bytotal internal reflection at the cavity wall 104a and prevented fromreaching the output fiber when the liquid is withdrawn from the cavity.For this purpose the liquid preferably has a refractive index that isapproximately equal to that of the housing material. Plastics that canbe used for the housing typically have a refractive index of about1.4-1.6, while glass has a refractive index of 1.47. An example of asuitable liquid is Fused Silica Matching Fluid from CargilleLaboratories, Inc., with a refractive index of 1.4587.

The piston 112 and open portion of the reservoir 106 are offset into orout of the page from the optical path between the input and outputfibers, and accordingly do not interfere with the light transmissionwhen the switch is ON. As with the other switches described above, theswitch of FIG. 12 can be actuated either mechanically orelectro-mechanically. A pair of GRIN lenses (not shown) are alsopreferably used with the input and output fibers to reduce losses.

The invention also includes improved optical oscillators for operatingdirectional signals and the like. Such an oscillator is shown in FIG.13, in which the input fiber 52a is shown aligned with and illuminatingthe output fiber 52b in its ON position, and illuminating aphotodetector 114 in its OFF position 52a'. The input fiber is normallyurged towards its OFF position by a mechanism such as coil spring 116.The illuminated photodetector 114 causes a device such as electromagnet118 to move the input fiber to its ON position; this is accomplished byproviding a magnetic sleeve 120 around the input fiber. Thephotodetector is preferably implemented as a solar cell that provides adirect electrical actuation of the electromagnet 118 through connectinglead wires 122, but it can also be formed as a more passivephotodetector that actuates a separate electrical drive for theelectromagnet.

In operation, the input fiber is normally in its OFF position 52a'.Until the oscillator is actuated, the solar cell 114 is prevented fromactuating electromagnet 118 by a suitable mechanism, such as a shutterbetween the solar cell and the input fiber, or by an electrical switchin the solar cell-electromagnet circuit. This inhibition is removed whenoscillator operation is desired, and the solar cell energizes theelectromagnet to shift the input fiber 52a into alignment with theoutput fiber 52b. The light transmitted through the input fiber thuscontinues on through the output fiber to the directional signal or otheroptical load, causing it to flash on. Once the light from the inputfiber has been removed from the solar cell, however, the spring 116restores the input fiber to its original position, at which the solarcell is illuminated but the output fiber is not. The input fiber thusoscillates back and forth between its OFF and ON positions, causing thedirectional signal to flash on and off.

A variation of this oscillator is illustrated in FIG. 14. Instead of thespring 116 and electromagnet 118, a bimetallic strip 124 is coupled tothe input fiber. The input fiber's normal OFF position is indicated indashed lines 52a', illuminating the solar cell 114. The solar cell isconnected directly to the bimetallic strip, and passes a heating currentthrough the strip when the oscillator is actuated. Heating the stripcauses it to flex, thus flexing the input fiber 52a into alignment withthe output fiber 52b. This in turn removes the illumination from thesolar cell, so that it allows the bimetallic strip to cool and torestore the input fiber back into alignment with the solar cell.Oscillation between the ON and OFF positions again continues for as longas the solar cell circuit is enabled. A suitable structure for thebimetallic strip is the industry standary ASTM Type TM2, preferably0.025 inch thick, 0.25 inch wide and 1.5 inch long. This strip should beheated to about 250° F. to produce an adequate flexing (about 1/4 inch)of the input fiber.

The invention also includes a failsafe system in which multiple lampsare used, with each lamp backing up another lamp in case it fails. Sucha system is illustrated in FIG. 15, with lamps 2a and 2b respectivelyilluminating optical fiber bundles 126a and 126b that respectivelyprovide light for a first set of optical loads 128a (such as the vehicleheadlights and tail lights), and for a second set of optical loads 128b(such as the vehicle's remaining optical devices). The light pathsbetween lamps 2a and 2b and their respective fiber bundles 126a and 126bare indicated by vectors 130a and 130b, respectively.

Respective partially reflective beam splitters 132a1 and 132b1 areprovided for the lamps 2a and 2b, and are normally held out of theoptical path between the lamps and fiber bundles. The beam splitters areactuated when the failure of one of the lamps is sensed. Numeroussensing mechanisms can be devised, such as optical fibers 134a and 134bthat are illuminated respectively by lamps 2a and 2b. The other ends offibers 134a and 134b are coupled to a photodetector system 136 thatsenses when one of the lamps has failed, and transmits correspondingelectrical control signals to the beam splitters over electrical lines138a and 138b.

The beam splitters 132a1 and 132b1 can each be pivoted to respectivesecond and third positions 132a2, 132a3 and 132b2, 132b3. In theirsecond positions, each of the beam splitters transmits a portion of thelight from their respective lamps to their respective fiber bundles, andreflect the rest of the light to the beam splitter for the other lamp,while in their third positions they reflect light from the other beamsplitter into their respective fiber bundles.

To understand the operation of the failsafe system, assume first thatthe lamp 2b has failed. This is sensed by the controller 136, whichcauses the first and second beam splitters to pivot respectively totheir second and third positions 132a2 and 132b3. In this position thepartially reflective first beam splitter transmits a portion of thelight from lamp 2a to its fiber bundle 126a and reflects the rest of thelight to the other beam splitter, with which it is now opticallyaligned. The second beam splitter in its position 132b3 reflects aportion of the light received from the first beam splitter to the fiberbundle 126b for the second beam splitter. The first beam splitterpreferably reflects about 62% of the light it receives to the secondbeam splitter, so that the two sets of optical loads 128a and 128breceive approximately equal illuminations.

If the first lamp 2a fails, the first beam splitter is pivoted to itsthird position 132a3, while the second beam splitter is pivoted to itssecond position 132b2. In these positions a portion of the light fromlamp 2b is reflected to the first beam splitter and from there into itsassociated fiber bundle 126a, with the remainder of the light from lamp2b is transmitted through the second beam splitter into its own fiberbundle 126b. Again, there is preferably an equal sharing of lightbetween the two sets of optical loads.

The efficiency of the described failsafe system is less than optimum,since not all of the light reflected from the surviving bulb will reachthe fibers for the failed bulb; a portion will escape through thepartially reflective beam splitter for the failed bulb. The opticalefficiency can be improved by providing two pairs of beam splitters thatare rotatable respectively to positions 132a2, 132a3, 132b2, and 132b3from initial positions outside the optical paths. By making the beamsplitters that are rotatable to positions 132a2 and 132b2 50% reflectiveand the beam splitters that are rotatable to positions 132a3 and 132b3fully reflective (i.e., mirrors), the loss of light through the lattertwo beam splitters can be substantially eliminated.

It can thus be seen that each lamp backs up the other in case offailure. To counteract the reduction in illumination that would normallyresult from splitting the light from one lamp between both sets ofloads, the controller 136 can also be set up to amplify the output fromthe surviving lamp. Control lines 140a and 140b that run from thecontroller respectively to lamps 2a and 2b are illustrated for thispurpose.

The invention can thus be seen to provide significant improvements for adistributed lighting system. While several illustrative embodiments ofthe invention have been shown and described, numerous variations andalternate embodiments will occur those skilled in the art. Suchvariations and alternate embodiments are contemplated, and can be madewithout departing from the spirit and scope of the invention as definedin the appended claims.

We claim:
 1. A lighting system for a vehicle that includes a pluralityof headlight assemblies, comprising:a light source, a plurality ofoptical loads, an optical fiber network extending from said light sourceto provide illumination for said optical loads, and at least one opticalswitch within said optical fiber network, each of said switchesincluding a respective input fiber from said light source and arespective output fiber to a respective optical load, said switchesoperating by selectively enabling or disabling an optical connectionbetween their respective input and output fibers, each of said headlightassemblies including:at least one headlight lens for transmitting aheadlight beam, a respective optical fiber of said optical fiber networkaligned with each lens to illuminate the lens for transmitting aheadlight beam, and means for adjusting the positions of said fibersrelative to their respective lenses to adjust the nature of theheadlight beam.
 2. The vehicle lighting system of claim 1, said fiberadjusting means for each headlight assembly comprising means for movingthe fibers in a generally vertical direction to switch between high andlow beam positions.
 3. The vehicle lighting system of claim 1, saidfiber adjusting means for each headlight assembly comprising means formoving the fibers toward and away from their respective lenses to adjustthe beam collimation.
 4. The vehicle lighting system of claim 1, eachheadlight assembly including a plurality of lenses and aligned fibers,said aligned fibers being held in a common mounting member, and a motorfor adjusting the position of said mounting member.
 5. The vehiclelighting system of claim 1, further including means for detecting lightwithin a predetermined wavelength from the opposite side of the lensesfrom said fibers, said adjusting means adjusting the positions of saidheadlight fibers in response to such detected light.
 6. The vehiclelighting system of claim 5, wherein said light detecting means respondsto light at a wavelength of the headlight beam to adjust the positionsof said headlight fibers.
 7. The vehicle lighting system of claim 6,wherein said headlight fiber position adjusting means moves the fiberswith respect to their respective lenses to increase the headlight beamdiffusion and/or lower the headlight beam in response to said lightdetecting means detecting light at said headlight beam wavelength. 8.The vehicle lighting system of claim 5, said light detecting meansincluding at least two light detectors that are laterally spaced fromeach other, and means for enabling said headlight fiber positionadjustment only in response to the ratio of light intensities detectedby said detectors corresponding to the reflection of said headlight beamfrom a vehicle in front in the same traffic lane and/or a distantoncoming vehicle in an adjacent traffic lane, but not to the detectionof a headlight beam from a nearby oncoming vehicle in the adjacenttraffic lane.
 9. The vehicle lighting system of claim 1, wherein theoptical fiber for each lens comprises an input fiber, and furthercomprising a plurality of output fibers for each lens, said outputfibers being located at different positions relative to their respectivelenses so that the lenses transmit headlight beams in differentdirections when illuminated by different ones of their respective outputfibers, and said means for adjusting the positions of said input fibersoperates by moving said input fibers between optical alignments withtheir respective output fibers.
 10. A lighting system comprising:a lightsource, a plurality of optical loads, an optical fiber network extendingfrom said light source to provide illumination for said optical loads,and at least one optical switch within said optical fiber network, eachof said switches including a respective input fiber from said lightsource and a respective output fiber to a respective optical load, saidswitches operating by selectively enabling or disabling an opticalconnection between their respective input and output fibers, at leastone of said optical switches, comprising:a housing having a pair ofintersecting fiber and shutter bores extending through the housing, apair of fiber pistons positionable in said fiber bore on opposite sidesof said intersection, said fiber pistons including means for holdingrespective input and output fibers in optical alignment with each other,an opaque shutter that is positionable within said shutter bore to blockthe transmission of light between said input and output fibers in aswitch OFF position, said shutter including a generally transmissivesection that enables the transmission of light between said input andoutput fibers when the transmissive section is positioned between saidfibers in a switch ON position, and a pair of shutter pistons mountingsaid shutter between them and movable through said shutter bore as aunit with said shutter between said switch OFF and switch ON positions.11. The lighting system of claim 10, further comprising a mechanicalcontrol means for controlling the position of said shutter pistonswithin said shutter bore.
 12. The lighting system of claim 10, saidshutter pistons being formed from a magnetic material, and furthercomprising a pair of electromagnets on opposite sides of said shutterpistons within said shutter bore, and means for selectively actuatingsaid electromagnets to control the positions of said shutter and shutterpistons within said bore.
 13. The lighting system of claim 10, furthercomprising first and second gradient index rod lenses respectivelybetween said input fiber and bore intersection and between said boreintersection and output fiber within said fiber bore, said lensesexpanding a light beam from the input lens and contracting the beam backinto said output fiber after transmission through said generallytransmissive shutter section with said switch in an ON position, saidlenses reducing light losses that would otherwise occur from forming ofa light beam emitted from said input fiber.
 14. The lighting system ofclaim 10, said generally transmissive shutter section comprising a colorfilter.
 15. A vehicle headlight assembly, comprising:at least oneoptical lens for transmitting a headlight beam, a respective opticalfiber aligned with each lens to illuminate the lens for transmitting aheadlight beam, and means for adjusting the positions of said fibersrelative to their respective lenses to adjust the nature of theheadlight beam.
 16. The headlight assembly of claim 15, said fiberadjusting means comprising means for moving the fibers in a generallyvertical direction to switch between high and low beam positions. 17.The headlight assembly of claim 15, said fiber adjusting meanscomprising means for moving the fibers toward and away from theirrespective lenses to adjust the beam collimation.
 18. The headlightassembly of claim 15, including a plurality of lenses and alignedfibers, wherein said fibers are held in a common mounting member, and amotor is provided for adjusting the position of said mounting member.19. The headlight assembly of claim 15, further including means fordetecting light within a predetermined wavelength from the opposite sideof the lenses from said fibers, said adjusting means adjusting theposition of said fibers in response to such detected light.
 20. Theheadlight assembly of claim 19, wherein said light detecting meansresponds to light at a wavelength of the headlight beam to adjust thepositions of said fibers.
 21. The headlight assembly of claim 20,wherein said fiber position adjusting means moves the fibers closer totheir respective lenses to increase the diffusion of the headlight beamin response to said light detecting means detecting light at saidheadlight beam wavelength.
 22. The headlight assembly of claim 19, saidlight detecting means including at least two light detectors that arelaterally spaced from each other, and means for enabling said fiberposition adjustment only in response to the ratio of light intensitiesdetected by said detectors corresponding to the reflection of saidheadlight beam from a vehicle in front in the same traffic lane and/or adistant oncoming vehicle in an adjacent traffic lane, but not to thedetection of a headlight beam from a nearby oncoming vehicle in theadjacent traffic lane.
 23. The headlight assembly of claim 15, whereinsaid optical fibers comprises input fibers, and further comprising aplurality of output fibers for each lens, said output fibers beinglocated at different positions relative to their respective lenses sothat the lenses transmit headlight beams in different directions whenilluminated by different ones of their respective output fibers, andsaid means for adjusting the positions of said input fibers operates bymoving said input fibers between optical alignments with theirrespective output fibers.
 24. An optical switch, comprising:input andoutput optical fibers having aligned but mutually spaced ends, an opaqueshutter between said fiber ends, said shutter including a generallytransmissive section, means for moving said shutter between a switch OFFposition with the shutter blocking the transmission of light betweensaid fibers, and a switch ON position with the shutter's generallytransmissive section aligned with said fibers and enabling thetransmission of light therebetween, and first and second gradient indexrod lenses respectively between said input fiber and shutter, andbetween said shutter and output fiber, said lenses expanding a lightbeam from the input fiber and contracting the beam back into said outputfiber after transmission through said generally transmissive shuttersection with said switch in an ON position, said lenses reducing lightlosses that would otherwise occur from fanning of a light beam emittedfrom said input fiber.
 25. The optical switch of claim 24, saidgenerally transmissive section comprising a color filter.
 26. Theoptical switch of claim 25, said shutter moving means including meansfor moving said shutter to intermediate positions between said OFF andON switch position, and thereby providing a dimming capability.
 27. Anoptical switch, comprising:a housing having a pair of intersecting fiberand shutter bores extending through the housing, a pair of fiber pistonspositionable in said fiber bore on opposite sides of said intersection,said fiber pistons including means for holding respective input andoutput fibers in optical alignment with each other, an opaque shutterthat is positionable within said shutter bore to block the transmissionof light between said input and output fibers in a switch OFF position,said shutter including a generally transmissive section that enables thetransmission of light between said input and output fibers when thetransmissive section is positioned between said fibers in a switch ONposition, and a pair of shutter pistons mounting said shutter betweenthem and movable through said shutter bore as a unit with said shutterbetween said switch OFF and switch ON positions.
 28. The optical switchof claim 27, further comprising a mechanical control means forcontrolling the position of said shutter pistons within said shutterbore.
 29. The optical switch of claim 27, said shutter pistons beingformed from a magnetic material, and further comprising a pair ofelectromagnets on opposite sides of said shutter pistons within saidshutter bore, and means for selectively actuating said electromagnets tocontrol the positions of said shutter and shutter pistons within saidbore.
 30. The optical switch of claim 27, further comprising first andsecond gradient index rod lenses respectively between said input fiberand bore intersection and between said bore intersection and outputfiber within said fiber bore, said lenses expanding a light beam fromthe input lens and contracting the beam back into said output fiberafter transmission through said generally transmissive shutter sectionwith said switch in an ON position, said lenses reducing light lossesthat would otherwise occur from forming of a light beam emitted fromsaid input fiber.
 31. The optical switch of claim 27, said generallytransmissive shutter section comprising a color filter.
 32. A failsafelighting system for multiple optical loads, comprising:at least twolight sources connected by optical fibers to respective optical loads,respective optical beam splitters associated with each of said lightsources for diverting a portion of the light from its respective lightsource to the optical load for another light source while continuing tosupply a portion of the light from its respective light source to itsown optical loads, so that both sets of loads are supplied by the samelight source, and actuating means responsive to the failure of one lightsource for actuating the beam splitter for the other light source. 33.The failsafe lighting system of claim 32, wherein the beam splitter foreach light source has a first non-actuated position, a second positionat which it diverts a portion of the light from its respective lightsource to the optical load for another light source, and a thirdposition at which it directs light diverted from another light source toits own optical load, said actuating means placing the beam splitter foreach of said light sources in its third position when the beam splitterfor the other light source is in its second position.
 34. The failsafelighting system of claim 33, wherein said beam splitters are rotatablebetween said first, second and third positions, with the second positionfor each beam splitter is optically aligned with the third position forthe other beam splitter to which it diverts light when the other beamsplitter's light source has failed.
 35. The failsafe lighting system ofclaim 32, wherein the beam splitter for each light source is moveablebetween a first position out of the optical path between its lightsource and optical load and a second position at which it diverts aportion of the light from its respective light source, and furthercomprising respective reflectors for each of said light sources that aremoveable between first positions out of the optical paths between theirlight sources optical loads, and second positions that are opticallyaligned with the second positions for the other light source's beamsplitter, said reflectors in their second positions reflecting lightfrom the beam splitter for the other light source into the optical loadfor their own light source.
 36. The failsafe lighting system of claim32, for a vehicle lighting system, wherein one light source normallyilluminates the vehicle's head and tail lights, and another light sourcenormally illuminates the vehicle's other lighting systems.
 37. Thefailsafe lighting system of claim 32, wherein the output intensitiesfrom said light sources is adjustable, and further comprising means forincreasing the output intensities of said light sources when a portionof their optical outputs is diverted to the optical load for anotherlight source.